Facile synthesis of three dimensional flower-like Co3O4@MnO2 core-shell microspheres as high-performance electrode materials for supercapacitors

In this work, we reported the synthesis of three dimensional flower-like Co3O4@MnO2 core-shell microspheres by a controllable two-step reaction. Flower-like Co3O4 microspheres cores were firstly built from the self-assembly of Co3O4 nanosheets, on which MnO2 nanosheets shells were subsequently grown through the hydrothermal decomposition of KMnO4. The MnO2 nanosheets shells were found to increase the electrochemical active sites and allow faster redox reaction kinetics. Based on these advantages, when used as an electrode for supercapacitors, the prepared flower-like Co3O4@MnO2 core-shell composite electrode demonstrated a significantly enhanced specific capacitance (671 F g−1 at 1 A g−1) as well as improved rate capability (84% retention at 10 A g−1) compared with the pristine flower-like Co3O4 electrode. Moreover, the optimized asymmetric supercapacitor device based on the flower-like Co3O4@MnO2//active carbon exhibited a high energy density of 34.1 W h kg−1 at a power density of 750 W kg−1, meaning its great potential application for energy storage devices.